1. Technical Field
The present invention relates to a method for repairing drainage pipes such as an obsolete sewer pipe.
2. Background Art
If a sewer pipe buried in the ground for a long time becomes obsolete to cause its load resistance or waterproofness to be degraded, then there will exist a problem in that a road may sink or a flow-down ability of the pipe may become insufficient.
As a method to solve such a problem, there has been proposed and performed a drainage pipe repairing method in which a resin pipe is placed in an obsolete sewer pipe by utilizing the sewer pipe as a supporting body to produce a new sewer pipe.
Among the various existing methods of repairing the above-mentioned drainage pipe, for example, there is a pipe manufacturing method in which a band-shaped rigid PVC material is supplied in a manhole, and then inserted into an existing pipe while being formed into a pipe shape at the inlet portion of the existing pipe by a pipe manufacturing machine.
Further, there is also known a so-called sheath pipe technique in which instead of the band-shaped rigid PVC material, a short pipe that is shorter in length and smaller in pipe diameter than those of the existing pipe is carried in from a manhole, and then inserted into the existing pipe while being successively connected.
However, the above-mentioned pipe manufacturing technique requires a work facility dedicated for the pipe manufacturing machine and the like, and also skilled workers to perform the technique. On the other hand, the above-mentioned sheath pipe technique requires no pipe manufacturing machine, but the sheath pipe has been manufactured as a pipe, so that the pipe is not easily handled within a narrow manhole.
Moreover, both the techniques require a connecting operation to form a pipe shell within an existing pipe, so that there also exists a problem in that substantial working time must be spent to improve the sealing of the connection portions.
Therefore, for example, Japanese Patent Application Laid-Open No. 2002-38581 discloses a method as a recent technique capable of simply forming a pipe shell within an existing pipe without requiring a dedicated work facility. In this technique, as shown in FIG. 9, a flexible resin pipe 50 is supplied from a rotating drum 51, inserted through a manhole 52 from one side of an existing pipe 53 by utilizing the flexibility of the resin pipe 50, and then taken up from the other side of the existing pipe 53 by means of a winch 54.
Further, in the figure, reference numeral 55 designates a cap mounted onto a head of the resin pipe 50, and reference numeral 56 designates a wire connected to the cap 55.
However, although the technique described in the above-mentioned Patent Publication uses the resin pipe 50 that is integrally made by forming, spirally or in a ring shape, corrugated portions having convex portions and concave portions (the convex portions are independent from each other) in the pipe axis direction thereof, or the resin pipe 50 that is integrally formed by making the surface thereof flat without convex portions and concave portions, priority is given to the flexibility over the tensile strength by taking the workability into account, so that there exists a problem in that when the resin pipe 50 is pulled roughly by the winch 54, an elongation of the pipe that exceeds the original length of the resin pipe may occur and cause the load resistance to be degraded.
Also, when an attempt is made to construct the resin pipe 50 inserted into a lengthy existing pipe as seamless pipe, there exists another problem in that the resin pipe 50 also becomes lengthy and thus the rotating drum 51 for winding up the lengthy resin pipe 50 becomes larger in size.
The present invention is made to consider problems in a conventional drainage pipe repairing method as described above; a first object of the invention is to provide a drainage pipe repairing method in which a resin pipe can be pulled in an existing drainage pipe without developing an elongation, and a second object thereof is to provide a drainage pipe repairing method in which a resin pipe inserted into an existing pipe can achieve a compact design.